Process for centrifugal casting



May 26, 1931. A. KEUP 1,807,536

PROCESS FOR CENTRIFUGAL CASTING Filed March 14, 1929 www MM,

`Patented May 26, 192,1

UNITED STATES ALBERT KEUP, OF GELSENKIRCHEN, GERMANY r'RocEss ron,CENTRIFUGAL CASTING Application led March 14, 1929, Serial No. 347,085,and in Germany .Tune 15, 1928.

My invention relates to centrifugal casting, particularly the casting ofiron and steel, and is applicable to the casting of either solid orcylindrical blocks.,

One form of the invention is illustrated by way of example in theaccompanying drawings, whereini Figure l is a vertical mid-sectionthrough the mold which is used,

Fig. 2 is an elevation partly in section of a complete apparatus forcasting in accord ance with the invention.

Heretofore solid ingots have been cast by pouring lmetal into a moldwhich is at rest.

Various defects in this method of casting are well-known in the art.This method of casting in a stationary mold permits all the slaglike andother impurities, which are distributed throughout the metal, to remainimprisoned therein. Pipes, blow-holes, and flaws are formed duringsolidiiication, which result in considerable loss in both quality andquantity of metal. Thus there is a high percentage of defects, and thecost of manufacture is therefore great.

A The present method avoids these disadvantagesby pouring the ingot in averticallylaced mold which rotates during casting. Rotation of the moldcauses a violent outward movementof the metalaway from the axis ofrotation, and solidification of the liquid metal takes place under theiniiuence of centrifugal force. During this action the lightersubstances contained in the liquid metal, including non-metallic andgaseous components which are deleterious to quality, are separated outof the metal with which they are mixed or are shifted to a positionwhere they may be readily removed. Centrifugal force causes the outwardmovement of the heavy metal to be cast and consequently the lightersubstances, including non-metallic and gaseous impurities which arecontained in the liquid metal, move inwardly and are separated out ofthe primary metal. This action gives the gases opportunity to escape andpermits the other impurities to be gradually iioated upward into theso-called lost head as the central surface of the liquid 5 metal rises.

In carrying out the present invention, it is preferred tostart thepouring when the mold is turning s lowly and to maintain a steady streamof metal into the mold. As the pouring proceeds the speed of rotation isgradually increased to a maximum which depends, of course, on thedimensions of the ingot being cast. I may bring the speed of rotation toa maximum after the metal has risen along the walls of the mold to itscover. Owing to the rotation and the action of centrifugal force, thereis formed in the molten metal in the mold a centrally-disposed hollowspace which extends downwardly in the form of a paraboloid from theupper surface of the metal. Slag, impurities, and gases work inwardlyand upwardly through the molten metal vinto this paraboloid. As thepouring and the rotation proceed this paraboloid rises so'that the ingotis cast gradually and is com- 70 pleted from below upward. This risepermits the apex 0f the paraboloid to be brought wholly up out of thelimits of the finished ingot; that is to say, up into the so-called losthead. Thus all of the impurities are brought out of that portion of theingot which is destined to be worked.

In the drawings there is shown, by way of illustration, a mold a whichis ada ted for use in carrying out the invention. pon the mold a thereis itted a cover b having a central tubular extension c thereon,preferably with a tapered opening. A frame d is provided for rotatablymounting the mold. Suitably mountediin the frame d is a revoluble chucke into which the base of the mold fits and with which the mold rotates.Suitable gearing is provided on the chuck e for meshing with gear unitf, which in turn is driven by a motor g. Thus when the motor g operatesthe chuck e, is rotated, and with it the mold a, which is held at alltimes in a vertical position.

The form of cover b may, of course be varied as desired, as it is notnecessary that 'there be a sudden break between the large diameter ofthe mold and the smaller diameter of the tubular extension c. Contraryto present practice in using covers 'for metallic molds, the cover b ispreferably of the same y liqu1d metal to the inner metal as that of themold and need not be warmed up prior to casting. However, the cover cmay be of refractory material in accordance with present practice.

Successive positions of the paraboloid, which has been referred toabove, are indicated by broken lilies in Figure l. Thus the tubularextension c upon the cover permits the gradual removal of the impuritiescontained in the metal 'as the pouring progresses. This is accompaniedby a decrease in the paraboloid cavity.

In casting hollow varied somewhat.

According to known practice in casting hollow ingots by the centrifugalmethod, after pouring the metal into almold which is held in thevertical position, the rotating mold is brought to a. horizontalposition and a considerable increase is given to the speed of rotation.By turning the mold into the horizontal position it has been attemptedto produce under the increased speed, a hollow ingot having walls whichare as uniform as possible. However, this method has never been' abletosecure a foothold in practice because it is too complicated anddifficult in operation. It is expensive and requires an excessivelyexpensive plant. The methodl has also remained without practicalsignificance because the products have not been satisfactory. Probablynowhere today are hollow ingots being cast by this method.

The present invention avoids the above mentioned disadvantages andproduces an ingot having a thoroughly dense and iiaw free texture. Itis, therefore, preeminently suited to th'e manufacture of the highestquality of hollow ingots.

According to the present invention, the liquid metal is poured from aladle into a vertically-positioned rotating mold. The mold is firstrotatedrat a very moderate speed. As the liquid metal is added, thespeed of rotation is steadily increased, care being taken that the speedand volume of metal poured into the mold are maintained at such araingots the procedure is tio that the metal does not rise along theinner wall of the mold in so thin a sheet that it solidifies-too soon.If the speed of rotation is increased too rapidly, certain defects inthe product will result: cracks and scale form which greatly diminish,or even prevent the further utilization of the hollow ingot. Thus it isbest to adjust the rate of pouring and speed of rotation to givesuiiicient time for the impurities and gases to escape through the wallof thel casting. In the present invention there is employed, of course,the known method of warming the mold, but this alone is far fromsuicient to eliminate the defects which vhave been mentioned, asexperiments have shown.

uring pouring the speed of rotation 1s maintained at a point where theWall thickness of the ingot is such that the lighter impurities, such asslag and gases, will not be caught and imprisoned by too rapid freezingof the metal, but will be given time to be pushed toward the inner wallof the casting by the force of the heavier metal which 'is being urgedoutward by centrifugal force. It may `be further noted that theprogressive freezing of the metallic mass from the outer surface inwardpromotes the movement of these impurities through the still iuid metalnearer the inner surface of the casting. EX- periments have alsodeveloped the fact that the gases escape from the metal more rapidly andcompletely in a vertically-positioned mold than in molds which arepositioned horizontally as in the past. In the latter case the greaterspecific gravity of the metal cannot react to separate the impurities tothe same extent as is possible in an upright mold. Hollow ingotsproduced according to the present invention show a wholly dense metallic structure.

lVhere actual slight variations in wall thickness are found they may beeasily rendered harmless by appropriate further treatment. However, suchvariations are not to be expected and are slight wherever they occur.The present process yields in particular a supremely dense material, sothat objects made therefrom will satisfy the strictest requirements asto quality.

It may be further mentioned that' as soon as the impurities in the metalhave ceased separating out and the metal has cooled to a certain degreeof rigidity, the cooling may be hastened by introducing into the centralhollow of the ingot a fluid, that is to say a liquid or gaseous coolingmaterial. This shortens the time during which the ingot must remain inthe mold, and the apparatus is made sooner available for the nextpouring.

With the understanding that the specific constructions illustrated andthe description here given are illustration,

I claim:

1. In a process for reducing metal ingots in a centrifugal mold) thesteps of pouring the metal into a vertically-placed mold while the moldis being slowly rotated, and gradually increasing the speed of rotationduring the pouring without decreasing the speed of rotation until thecasting is made.

In a process for producing metal ingots by centrifugal casting, thesteps of pouring the metal into a vertically-placed mold While the moldis being slowly rotated, gradually increasing the speed of rotationduring pouring, and proportioning the rate of pouring and speed ofrot-ation to maintain such a ratio that the metal does not rise alongthe iflall of the mold to form a quickly solidified s eet.

presented merely by way of 3. In a process for producing metal ingots ina centrifugal mold, the steps of pouring the metal into avertically-placed mold while the, mold is being slowly rotated,gradually increasing the s eed of rotation during pouring, adjusting therate of pouring and speed of rotation to give suiiicient time for theimurities and gases to escape through the iquid metal to the inner Wallof the casting,

and accelerating coolin of the resulting ingot by introducing a uidcooling medium into its hollow portion.

4. In a process for producing metal ingots in a centrifugal mold, havingla cover, the

steps of pouring the metal into a verticallyplaced mold while the moldis being slowly rotated, gradually increasing the speed of rotationduring the pouring, bringing the speed of rotation to a maximum afterthe metal has risen along the walls of the mold to its cover, andaccelerating cooling of the resulting ingot by introducing a fluidcooling medium into its hollow portion.

5. In a process for producing metal ingots by centrifugal casting, thesteps of slowly rotating an empty mold on a vertical axis, pouringmolten metal into the slowly rotating mold, gradually increasing thespeed of rotation until the metal has risen along the walls of the moldto a point adjacent its top, and continuing the pouring with a steadymaximum speed of rotation until the ingot is cast.

In testimony whereof I have signed my name to this specification.

ALBERT KEUP.

